The present invention relates to hydraulic systems mounted on trucks or similar vehicles to deliver hydraulic fluid, sometimes referred to as wet kit installations, such as used in tractor/trailers or trucks known as end dumps, side dumps, walking floors, tankers, low boys or similar vehicles. An example is shown in U.S. Pat. No. 7,913,713, incorporated by reference.
Common problems of such hydraulic systems are evidenced when the hydraulic fluid overheats, which can be indicative of other root causes of the hydraulic overheating on the tractor/trailer. In response to the overheating problem, some hydraulic systems have temperature switches which sense the temperature of the hydraulic fluid and turn the hydraulic system off if the sensed temperature exceeds a threshold value. By turning the hydraulic system off, often an underlying problem can be identified and corrected before a catastrophic overheating failure occurs. However, inoperability of the hydraulic system due to the overheating shut-off typically occurs at an inopportune time and location.
Hydraulic switching blocks can include one or more pressure relief mechanisms (such as pressure relief valves) that prevent fluid pressure within a portion of the hydraulic circuit from exceeding a threshold pressure value. When the hydraulic circuit powers the cooling fan as well as a working load, a pressure relief valve may be used to reduce the pressure used to drive the cooling fan. When a hydraulic circuit serves more than one device at the same time, the circuit designer may determine that the hydraulic circuit should share the hydraulic fluid on some basis of priority. Depending upon what other working load is being driven, and the cooling fan may or may not be considered a priority usage of the hydraulic fluid.